NASA Clears Shuttle Discovery for Friday Landing, Eyes Weather

STS-116 shuttle pilot William Oefelein, backdropped by the flag of his home state Alaska, gives students an OK sign as he and his crewmates spoke with a Challenger Learning Center of Alaska.Credit: NASA TV.

NASA is bringing
up two backup landing sites in California and New Mexico in addition to
Discovery's primary target here at the Kennedy Space Center (KSC).

Discovery's
STS-116 crew is due to land at KSC's Shuttle Landing Facility at about 3:56
p.m. EST (2056 GMT), but carry enough supplies to hold out until Saturday if
required [image].

The
astronauts are completing a 13-day
mission to the International
Space Station (ISS), where they rewired
the orbital laboratory's power grid, ferried a new
crewmember to join its Expedition 14 crew and installed
a new piece of the outpost's main truss. Earlier today, the crew deployed a
small experimental satellite dubbed ANDE to measure the effects of atmospheric
drag on spacecraft [image].

Landing
preparations

The threat
of rain -- which can damage shuttle heat shields if flown through -- and low
clouds currently plague a planned KSC landing. High winds anticipated at California's Edwards Air Force Base are also a concern Friday.

At NASA's
third landing option - Northrup Strip at White Sands Space Harbor in New Mexico - the weather Friday is expected to be acceptable, but the runway lacks
much of the basic hardware and infrastructure to handle an orbiter after it
returns to Earth.

Discovery's
commander said Thursday that he's playing no favorites.

"We've
trained extensively at all three sites, so we're very familiar with all of
them," Polansky told ABC News in an interview on NASA TV. "We would hope
to go to Florida and KSC. That's where the vehicle will be processed for its
next mission, that's where our families will most likely be waiting for us, so
that's always a plus."

NASA has landed
an orbiter at White Sands' Northrup Strip only once in its 25-year
history of shuttle flight during the STS-3 mission in 1982 aboard Columbia,
which suffered brake damage and extensive contamination from gypsum dust.

Since then,
a new towing area and concrete pad have been installed to protect the orbiter
against the dust from the gypsum-covered lakebed runway [image].

"So we feel
really good that the gypsum problem is taken care of once we get the vehicle
off the lakebed," Shannon said, adding that runway is flat and laser-leveled. "It
is just one of the best places you'd ever want to land anything."

NASA
officials expect it would take between 45 and 60 days to return Discovery to
KSC from White Sands, as compared to the traditional week of extra activity
required to safe an orbiter at Edwards, hoist it atop its modified 747 jet
carrier craft for the ferry ride back to its Florida launch site.

Shuttle
return rundown

Norm
Knight, NASA's entry flight director for Discovery's Friday landing, said
shuttle's first landing opportunity opens during orbit 202 here at KSC, and
requires the orbiter to fire its engines at 2:48 p.m. EST (1949 GMT) to make a
3:56 p.m. EST to touchdown in Florida.

If
Discovery's crew waits until their 203rd orbit to land, they could
aim first for Edwards and then preferably KSC around 5:30 p.m. EST (2230 GMT),
though White Sands is also available on that pass.

Additional
landing opportunities arise during the shuttle's next orbit, first at 7:00 p.m.
EST (0000 Dec. 23 GMT) at Edwards, and then on White Sands' Northrup Strip two
minutes later.

One last
landing opportunity at Edwards during Discovery's 205th Earth orbit would
put touchdown at 8:36 p.m. EST (0136 Dec. 23 GMT) before its crew would have to
reset for Saturday.

"The
strategy going into tomorrow is to pick a safe landing site," Knight said. "And
if it's safe to do so, we will land the vehicle."